(1) Field of the Invention
The invention relates to processes for treating tobacco and more particularly to an improved process for expanding and drying tobacco.
(2) Brief Description of the Prior Art
It is known in the prior art to expand tobacco with pressurized carbon dioxide, to subsequently reduce the pressure to solidify the carbon dioxide within the tobacco structure, to heat the tobacco to vaporize the solid carbon dioxide and to then dry the expanded tobacco. It also is known in the prior art to cool and even to freeze tobacco prior to further processing.
For example expired U.S. Pat. No. 3,223,090, inventor, D. G. Strubel et al and issued on Dec. 14, 1965, teaches flash freezing tubing filled with water-tobacco mixture by immersing the tubing in a liquid nitrogen or dry ice prior to further processing of the tobacco.
Unexpired U.S. Pat. No. 4,165,618, inventor, Lewis Tryee, issued Aug. 28, 1979; teaches treating tobacco products with a recoverable liquid cryogen such as nitrogen or carbon dioxide at equilibrium to minimize leaching of the tobacco components.
Unexpired U.S. Pat. No. 4,258,729, inventor, Roger Z. de la Burde et al, issued Mar. 31, 1981, teaches "presnowing" tobacco with finely divided solid carbon dioxide prior to gaseous carbon dioxide treatment in amounts of 5-50% by weight of tobacco to increase the amount of carbon dioxide retained by the tobacco.
Unexpired U.S. Pat. No. 4,289,148, issued to Klaus-Dieter Ziehn on Sept. 15, 1981, teaches treating tobacco with nitrogen or argon at preselected temperatures and pressures, releasing the pressure and then heating the tobacco at preselected temperatures.
Unexpired U.S. Pat. No. 4,235,250, inventor, Francis V. Utsch and issued on Nov. 25, 1980, and the two unexpired U.S. Pat. Nos. 4,258,729 and 4,333,483, inventors, Roger Z. de la Burde, Patrick E. Aument, and the same Francis V. Utsch, all teaching presnowing tobacco with finely divided solid carbon dioxide prior to gaseous carbon dioxide treatment in amounts of 5-50% by weight of tobacco to increase the amount of carbon dioxide retained by the tobacco.
As can be seen from the above, certain of the prior art practices of treating tobacco materials have taught the utilization of a liquid nitrogen bath and other practices have taught the utilization of a carbon dioxide treating step in either a gaseous or solid form. However, none of the past practices have suggested the novel process of the present invention which combines the steps of liquid nitrogen treatment, gaseous carbon dioxide treatment and drying with gases with temperature at least above about 250.degree. F. with wet bulb temperatures in the range of at least about 150.degree. F. to a maximum of 212.degree. F. in a tobacco treating process which requires a minimum of time, equipment and other operating costs and which, at the same time, provides an improved, homogenous tobacco product having a comparatively high fill value improvement with comparatively substantially equal or sometimes even lower alkaloids and total sugars losses.